In mammography it has been established that a causal relationship exists between breast tissue composition and increased risk of cancer.
In an article by R. Highnam et al. entitled ‘Breast composition measurements using retrospective standard mammogram form’ published in Phys. Med. Biol. 51 (2006) 2695-2713 it has been published that measures of breast tissue composition may serve as biomarkers for breast cancer risk. The composition measure that is most studied is the percentage of dense breast tissue in the breast. Typically the ratio of the area judged to be of dense nature and the area of the whole projected breast is evaluated. This ratio is classified into a number of categories such as the BI-RAD classification (ACR 1998). Another classification system known in literature is the Wolfe system.
When digital mammographic images are generated, the pixel value in a pixel depends on the characteristics of the x-ray image digitizer that is used, on the applied radiation dose at image recording and on the radiation absorption of the breast.
Typically the radiologist is interested in the radiation absorption of the breast and wants to eliminate the other factors.
A so-called SMF representation of an x-ray mammogram is a standardized quantitative representation of the breast from which the volume of non-fat tissue and breast density can be easily estimated.